There are a number of people who believe the Node 2i makes a great streamer in and of itself and adding the external DAC brings it to a whole new level. And as you know the Bluesound app is great.
The DAC in the 2i really is just ok once you have compared it with a good external DAC. I wish I could recommend a good budget DAC for you but I have only heard and use with my 2i an older Museatex Meitner Bitstream DAC modded by an individual who originally worked with Meitner, so no real frame of reference with the new improved flavors. But I think you are on a good path forward looking for a good new DAC.
The DAC in the 2i really is just ok once you have compared it with a good external DAC. I wish I could recommend a good budget DAC for you but I have only heard and use with my 2i an older Museatex Meitner Bitstream DAC modded by an individual who originally worked with Meitner, so no real frame of reference with the new improved flavors. But I think you are on a good path forward looking for a good new DAC.